This application is a 35 USC application of PCT/DE 00/03597 filed on Oct. 12, 2000.
1. Field of the Invention
The invention is based on an injector for a fuel injection system for internal combustion engines, having a nozzle needle protruding into the valve control chamber.
2. Description of the Art
Injectors that are controlled by a magnet valve or a piezoelectric actuator are known. Regardless of the type of control, improvements in emissions and fuel consumption as well as noise produced by the internal combustion engine can be attained, among other provisions, by shortening the control times of the injectors. Shortened control times mean that the metering of the injection quantities is done more precisely, and that the course of injection can be designed with greater freedom. Finally, in modern internal combustion engines in motor vehicles, the available space is increasingly tight, which demands injectors of compact structure.
It is the primary object of the invention to furnish an injector for a fuel injection system for internal combustion engines whose control times are shortened and whose external dimensions are especially compact.
This object is attained according to the invention by an injector for a fuel injection system for internal combustion engines, having a valve control chamber controlling a nozzle needle, in which the valve control chamber is defined by an end face of the nozzle needle.
This injector has the advantage that by the omission of a long thrust rod and a valve piston, the number of components and the mass inertia of the moving parts of the injector are reduced. This makes short control times possible. In addition, the valve control chamber can be brought closer to the injection nozzle, making thinner nozzle needles possible as well. This effect contributes to a further reduction in the moving masses inside the injector.
With the omission of multiple components and the possible reduction in size of the components that remain, a marked reduction in the structural size of the injector is attained. The diameter ratios of the injector of the injection are approximately equivalent to those of an injection nozzle of the prior art.
Furthermore, in the version of the injector according to the invention, no leakage can occur in the closed state, so that there is also no need to provide a leaking oil outlet.
In a variant of the invention, it is provided that the valve control chamber is disposed in a valve body, so that the injector can be produced simply and economically.
In another version of the invention, the valve body protrudes into a pressure chamber, so that a compact design of the injector is attained and the number of sealing points remains low.
The invention furthermore provides that the pressure chamber communicates with a high-pressure fuel reservoir via an inlet conduit; that the valve control chamber communicates at least indirectly with a high-pressure fuel reservoir via an inlet throttle; and that the valve control chamber communicates with the pressure chamber via an inlet throttle, so that the requisite hydraulic connections between the valve control chamber, pressure chamber and high-pressure fuel reservoir can be achieved in a simple way.
The invention also provides that the valve control chamber can be made to communicate with a fuel return, via an outlet conduit, an outlet throttle, and a control valve, in particular a 2/2-way control valve or 2/3-way control valve, so that the pressure in the valve control chamber can be reduced by opening the control valve. As a consequence, the nozzle needle uncovers the sealing seat, and the injection begins.
A variant of the invention provides that the outlet conduit and an outlet throttle are disposed in the valve body, so that a further reduction in the requisite installation space is attained.
Further features of the invention provide that a closing spring braced against the valve body and at least indirectly against the nozzle needle is present in the pressure chamber; the closing spring is braced against a shoulder of the nozzle needle; or that a closing spring braced against the injector and against the nozzle needle is present in the valve control chamber, so that in the absence of fuel pressure the injector is always closed, and thus the uncontrolled outflow of fuel into the combustion chamber is prevented.
In one embodiment of the invention, it is provided that the diameter of the end face of the nozzle needle is greater than the diameter of the sealing line between the nozzle needle and a nozzle needle seat, so that for the same pressure in the valve control chamber and pressure chamber, the resultant hydraulic force always brings about a closure of the injector.
Further in the invention, it is provided that the control valve is actuated by a piezoelectric actuator, so that the control times of the injector of the invention are shortened further.
The object stated above is also attained by a fuel injection system for internal combustion engines, having a high-pressure fuel pump and having at least one injector having a valve control chamber controlling a nozzle needle, characterized in that the valve control chamber is defined by an end face of the nozzle needle, so that the fuel injection system of the invention can be used in internal combustion engines in which both a compact design and very short control times are required.
In a variant of the invention, the fuel injection system has a high-pressure fuel reservoir, so that the advantages of the injector according to the invention also benefit common rail fuel injection systems.